Retractable cord reels are commonly used in a wide variety of applications involving a wide range of environmental conditions, electrical signal types and numbers, and expected or required extension/retraction cycles. For example, retractable cord reels may be used in hazardous environments such as those that expose the cord reel to explosive gases, combustible fluids, etc., may be used in wet environments such as marine or other outdoor environments, may be used in environments that expose the cord reel to other contaminants such as dust, corrosive gases, oil, etc., to name a few. Additionally, some cord reels are used in applications involving a relatively large number of low power signals such as, for example, telephone applications, data transmission applications, etc. Many of these low power applications subject the cord reel to a relatively large number of extension/retraction cycles. Other cord reel applications involve a relatively small number of high power signals such as, for example, line voltage extension cord applications.
In any event, conventional retractable cord reel devices typically include a fixed portion of electrical cable and an extendable portion of cable. The extendable portion of electrical cable is usually wound on a spring-loaded spool and, thus, may be withdrawn or extended from the cord reel and, if desired, retracted back into the cord reel. As the extendable cable portion is withdrawn, it typically rotates the spool against the force of a spring. The energy stored in the spring may subsequently be used to rotate the spool in the opposite direction to retract the extendable cable portion into the cord reel. Of course, providing a continuous electrical connection between the fixed and extendable cable portions is not a simple matter, particularly due to the relative rotation between the fixed cable portion and the spool carrying the extendable cable portion.
Some known retractable cord reels utilize rotating contacts such as, for example, brushes and commutating rings, to provide electrical continuity between the fixed cable portion and the rotating spool on which the extendable cable portion is wound. With these types of cord reels, the extendable cable portion is usually electrically coupled to commutating rings that are integral to the rotating spool and the fixed cable portion is electrically coupled to brushes that are fixed to the cord reel housing and urged against the commutating rings. Unfortunately, such moving or rotating contacts are subject to wear and, thus, significantly reduce the life cycle of the cord reel. Further, these moving or rotating contacts have a propensity to generate sparks, which is unacceptable for use in hazardous environments and are prone to contamination from dirt, dust, liquids, etc. that may be common in many cord reel applications. Still further, rotating or moving contacts are electrically noisy, difficult to shield from environmentally induced noise and, as a result, are generally unsuitable for carrying low power, low-level signals.
More recently, some cord reels have been developed that eliminate the need for moving or rotating contacts. These cord reels utilize a substantially continuous cable having a flat portion and a round portion. The round portion of the cable is wound on a rotatable spool and the flat portion of the cable is spirally wound in an expansion chamber adjacent to a hub of the spool. As the round cable portion is withdrawn or extended form the cord reel, the spirally wound flat cable portion first unwinds or expands and then is rewound or contracts about a hub or other feature of the spool. One example of such a cord reel is disclosed in U.S. Pat. No. 6,372,988 to Burke et al.
While cord reels having a substantially continuous electrical cable including a round extendable portion and a flat fixed portion have proved useful in a wide variety of applications including, for example, applications involving telephone signals, audio signals, data signals, etc., the cable used in such devices is typically relatively complicated and expensive to manufacture. Furthermore, while the types of cables used for many low power applications such as those noted above can be formed to have a relatively flat portion and a relatively round portion along a continuous length of cable, many cables such as, for example, heavy-gauge power cables are difficult, if not impossible, to modify in this manner. Still further, due to safety requirements, much heavy gauge flat cable utilizes a relatively thick and rigid jacket or insulation. As a result, a fixed portion made of such heavy gauge cable may fail prematurely, because when it transitions between the contraction and expansion modes within the expansion chamber bending stresses are typically concentrated at a single point or area of the cable over an approximately one hundred-eighty degree bending cycle.